The world's largest vaccine producer had halted exports in April to cater to domestic demand as infections shot up.
The announcement comes as Prime Minister Narendra Modi visits Washington on Tuesday for a summit of the Quad leaders - US, India, Japan and Australia.
Officials say vaccines exports are likely to be discussed at the meeting.
Mr Mandaviya said India's vaccine manufacturers "are expected to produce more than 300 million doses" in October for the country's own vaccination drive and that any surplus supplies would be sent to other countries in the global fight against Covid-19.
"We will help the world, and through Covax we will also fulfil our responsibility," he told reporters on Monday.